Method For Reducing Negative Effects Of Adhesive Contaminants In Systems Of Substances Comprising Waste Paper

ABSTRACT

The invention relates to a method for reducing the negative effects of adhesive contaminants in the processing of waste paper, wherein an aqueous polymer dispersion comprising one component A and one component B for coagulation and detackification of stickies is added during the processing of waste paper, wherein component A is a homo- and/or copolymer of methyl methacrylate, acrylate and/or styrene and component B is a styrene copolymer having acrylic acid, maleimide and/or maleic acid hydride. The polymer dispersion can optionally comprise another component C, a cationic fixing agent that supports the coagulation of the stickies.

The invention relates to a method for reducing the negative consequencesof sticky contaminants (“stickies”) in the processing of waste paper andcoated broke in papermaking.

The returning of paper wastes from natural fiber stocks for aneconomically rational renewed use is state of the art. The operation ofpapermaking using waste paper is increasingly being hindered by stickycontaminants. As a result of the increased introduction of mixed wastepaper as a raw material source in papermaking, large amounts of solid orwater-soluble, tacky constituents are being introduced into the papermachine circuits. Adhesives from self-adhesive labels, hotmelts, tackycoating constituents on recycled coated papers and cartons, etc., arenot being removed completely by sorting, in spite of ever greatermechanical cleaning efforts.

They constitute a key cause of what are called “stickies” and “whitepitch”, whose hydrophobic properties mean that they frequently depositon hot parts and moving parts and on the wires and felts of papermachines, and may therefore lead to paper web breakages.

Stickies are sticky deposits in the form of organic complexes which formfrom the waste paper by agglomeration of interacting contaminants. Allsticky deposits introduced exclusively by the raw materials are termed“primary stickies”. Where, by contrast, the sticky impurities are formedonly as a result of reaction with additives, generally with cationicproduction assistants such as Al salts, anticontaminants,polyacrylamides, wet strength agents or else cationic starch, forexample, these deposits are termed “secondary stickies”. Considered aprincipal source of sticky contaminants are the adhesives from paperprocessing, but also synthetic binders from paper finishing.

In order to ensure effective treatment of sticky contaminants, the sizedistribution of the sticky contaminants is critical with respect to thethermal, chemical and/or mechanical methods that are to be employed.

A rough distinction is made between “macrostickies”, which are coarsesticky constituents having particle sizes of more than 150 micrometers,and that can largely be removed from the stock circuit by means ofstated separation procedures, and “microstickies”, which are fine stickyconstituents between 1 micrometer and 150 micrometers.

For years there have already been products supplied as passivatingagents for treating adhesive contaminants such as stickies. Thesedissolved products are intended to make the surface of the tackyimpurities more hydrophilic and hence keep them more wettable, therebyreducing the affinity for hydrophobic surfaces. Hydrophobic surfaces arepresent on, for example, wires, felts and rollers; hydrophobizing isboosted further by coating, with sizing agent or defoamer, for example,thereby further promoting the attachment of stickies.

In certain cases, microstickies do not cause any problems in papermakingif they do not agglomerate. In order largely to prevent reagglomerationof the microstickies, various methods are known for chemically modifyingthe stickies that have remained in the stock stream and the absorptionthereof on support materials of high specific surface area and also onthe fiber stock.

In the context of these problems, the procedures below have been adoptedin practice, but lead only to partial success.

On the one hand, dispersion may take place, with the aim of changing thecharge on the stickies by means of anionic and nonionic dispersants.This forms colloidal, anionically charged or nonionic particles whichcounteract agglomeration and deposition. The wetting properties of thedispersant are very important in this case, since the stickies aregenerally hydrophobic

Alternatively, the tack of the stickies can be reduced:

-   -   Fixing of the strongly anionic contaminants by means of strongly        cationic fixatives (formation of what are called polyelectrolyte        complexes; the reaction product then goes on to the anionic        fiber).    -   Absorption on pigments of high specific surface area (e.g.,        talc, modified clay, mica, smectite, bentonite), often with        subsequent flocculation by means of polymers in order to bind        separable macro-flocs.    -   Enveloping (masking) with nonionic hydrophilic polymers        (polyvinyl alcohol) or zirconium compounds, more particularly        zirconium acetate and ammonium zirconium carbonate.

Known strongly cationic fixatives include polyethyleneimine (PEI),polydiallyldimethylammonium chloride (polyDADMAC), polyvinylamine(PVAm), polyaluminum chloride (PAC), polyacrylamide (PAAM), polyamine,etc. The sphere of action of fixatives extends from about 1 nm to 50micrometers in terms of the particle size of the microstickies,depending on the nature and modification of the chemicals used.

Materials with a low surface energy (wires, felts, roller surfaces)exhibit a more hydrophobic behaviour and therefore possess a highaffinity for hydrophobic compounds, such as stickies, thereby resultingin contamination of the wires and hence to defects and/or reduction inthe dewatering performance of felts.

Adsorbents used are, in particular, various types of talc with specificsurface modifications and particle-size distribution, which on accountof their hydrophobic and organophilic surface are capable of attachingto adhesive constituents and entraining them with the paper. Particlesof adhesive encapsulated in this way have less of a tendency to depositon hot machinery parts. Using talc to control sticky deposits, however,has certain disadvantages. For instance, the system is highly sensitiveto shear. Talc, moreover, has poor retention properties and frequentlycauses clogging of the felts. Talc may adversely affect resin sizing,and stabilizes foam. The two inorganic products, talc and bentonite,require laborious dispersion.

Protein solutions as well are employed as agents for masking stickyimpurities.

The stickies lead to deposits on machinery parts, wires, cloths, dryingcylinders, and consequently to marks, holes, and instances of websticking, and consequently to breakages in the wet section and dryingsection in the course of winding and rewinding or in the course ofprinting.

There continues to be a need for improvement in reducing the tackinessof stickies.

Surprisingly, the tackiness of stickies can be reduced considerablythrough the use of a specific polymer dispersion.

The invention provides an aqueous polymer dispersion and the use thereofin a method for reducing sticky contaminants in the processing of stocksystems comprising waste paper, which comprises, when processing wastepaper, adding an aqueous polymer dispersion comprising a component A anda component B for coagulating and detackifying the stickies, component Abeing a homopolymer and/or copolymer of

acrylic acid and/or its alkyl esters, more particularly its methyl,ethyl, butyl, isobutyl, propyl, octyl, decyl, 2-ethylhexyl esters;or methacrylic acid and/or its alkyl esters, more particularly itsmethyl, ethyl, butyl, isobutyl, propyl, octyl, decyl, 2-ethylhexylesters;styrene and/or methylstyrene;vinyl acetate;itaconic acid;glycidyl methacrylate;2-hydroxyalkyl (meth)acrylate;methacrylamide;N-hydroxyethyl (meth)acrylamidedimethacrylate monomers, such as, for example, 1,4-butylene glycoldimethacrylate, 1,3-butylene glycol dimethacrylate, ethylene glycoldimethacrylate, diethylene glycol dimethacrylate, propylene glycoldimethacrylate, dipropylene glycol dimethacrylate,4-methyl-1,4-pentane-diol dimethacrylate;divinylbenzene and/or trivinylbenzeneand component B being a styrene copolymer with acrylic acid, maleimideand/or maleic anhydride.

Component A is a hydrophobic homopolymer and/or copolymer of theabove-stated monomers having a very high glass transition temperature orsoftening temperature (Tg), preferably methyl methacrylate. The glasstransition temperature of A is preferably above 40° C., moreparticularly above 80° C., very preferably above 100° C.

Component B is a styrene copolymer with (meth)acrylic acid, maleimideand/or maleic anhydride. Component B is preferably a copolymer ofstyrene and acrylic acid. Component B preferably has a molecular weightof between 3000 g/mol and 15 000 g/mol, more particularly 3000 and 7000g/mol.

Particularly preferred is an aqueous dispersion with particle sizes ofless than 150 nm, preferably less than 120 nm.

The aqueous polymer dispersion may optionally further comprise acomponent C, a cationic fixative, which promotes coagulation of thestickies. Component C is preferably selected from the following group:

polyethyleneimine (PEI), polydiallyldimethylammonium chloride(polyDADMAC), polyvinylamine (PVAm), polyaluminum chloride (PAC),polyacrylamide (PAAM), and polyamine.

In order to boost the efficiency of the polymer dispersion of theinvention and its stability, it is further possible to add a furthercomponent D optionally in the form of a surfactant.

Further to components A, B, C and/or D, the polymer dispersion compriseswater (component E).

In one preferred embodiment the aqueous dispersion comprises

2% to 50%, preferably 5% to 30% of component A,2% to 30%, preferably 5% to 25% of component B,0% to 2% of component C,0% to 0.3%, preferably 0% to 0.2% of component D, and96% to 17.7%, preferably 90% to 45% of water (component E).

All percentages here relate to % by weight.

In the presence of Ca²⁺, the aqueous dispersion constitutes aself-coagulating nanodispersion. The polymer dispersion of the inventionattaches to the hydrophobic sticky particles, incorporating them intothe precipitating polymer dispersion and thus detackifying them.

Surprisingly it has emerged that when using the polymer dispersion ofthe invention, the entrainment of stickies during the flotationprocedure is considerably improved. The polymer dispersion is preferablyadded before the deinking procedure. In this case, a second meteringpoint in the completed DIP (deinking pulp following mechanicalprocessing and, where appropriate, removal of coarse stickies) isadvisable. The amounts for use are between 0.5-2 kg/t of commercialproduct. When producing critical coated or impregnated specialty papers,it is advisable to add the polymer dispersion of the invention directlyto the coated broke. A further advantage of this polymer dispersion ofthe invention is that in pulp production it is thereby possible to dowithout inorganic adsorbents, such as talc, bentonite, cationizedfillers, and so on.

Since when using the polymer dispersion described it is not necessary toemploy any additional cationic components for coagulating themicro-stickies, these microstickies instead undergoing self-coagulationsimply at standard water hardnesses, and so surrounding the tackystickies, the method of the invention is notable, in comparison to theprior-art methods, for a high level of economic and environmentalbenefit.

EXAMPLES Example 1 Version with Methyl Methacrylate

A 2 l reactor with stirrer and reflux condenser was charged with 739.5 gof deionized water and 419.3 g of 25% strength solution ofstyrene-acrylic acid copolymer, this initial charge then being heated to85° C. with stirring under a nitrogen atmosphere.

Feed stream I:

384.8 g of methyl methacrylate

Feed stream II:

1.9 g of ammonium peroxodisulfate136.3 g of deionized water

When an internal temperature of 85° C. had been reached, feed stream Iand feed stream II were metered continuously into the polymerizationbatch via two separate feeds, beginning simultaneously, over a period of3 h 30, with stirring and retention of the reaction temperature. Thepumps were flushed with 318.2 g of deionized water. After the end ofboth feed streams, the system was left to afterreact at the reactiontemperature for a further 25 minutes. After that, the reaction mixturewas cooled to room temperature and filtered on a filter having a meshsize of 160 μm.

The characterization of the copolymer obtained, in terms of solidscontent (SC) and average particle size (D), is given below:

SC=24.1% D=53 nm Example 2 Version with Methyl Methacrylate+Crosslinker

A 2 l reactor with stirrer and reflux condenser was charged with 739.5 gof deionized water and 419.3 g of 25% strength solution ofstyrene-acrylic acid copolymer, this initial charge then being heated to85° C. with stirring under a nitrogen atmosphere.

Feed stream I:

370.9 g of methyl methacrylate19.5 g of glycidyl methacrylate

Feed stream II:

1.9 g of ammonium peroxodisulfate136.3 g of deionized water

When an internal temperature of 85° C. had been reached, feed stream Iand feed stream II were metered continuously into the polymerizationbatch via two separate feeds, beginning simultaneously, over a period of3 h 30, with stirring and retention of the reaction temperature. Thepumps were flushed with 318.2 g of deionized water. After the end ofboth feed streams, the system was left to afterreact at the reactiontemperature for a further 25 minutes. After that, the reaction mixturewas cooled to room temperature and filtered on a filter having a meshsize of 160 μm.

The characterization of the copolymer obtained, in terms of solidscontent (SC) and average particle size (D), is given below:

SC=24.9% D=40 nm Example 3 Version with Methyl Methacrylate+SecondCrosslinker

A 2 l reactor with stirrer and reflux condenser was charged with 740 gof deionized water and 419 g of 25% strength solution of styrene-acrylicacid copolymer, this initial charge then being heated to 85° C. withstirring under a nitrogen atmosphere.

Feed stream I:

370 g of methyl methacrylate19 g of ethylene glycol dimethacrylate

Feed stream II:

2 g of ammonium peroxodisulfate136 g of deionized water

When an internal temperature of 85° C. had been reached, feed stream Iand, feed stream II were metered continuously into the polymerizationbatch via two separate feeds, beginning simultaneously, over a period of3 h 30, with stirring and retention of the reaction temperature. Thepumps were flushed with 318 g of deionized water. After the end of bothfeed streams, the system was left to afterreact at the reactiontemperature for a further 25 minutes. After that, the reaction mixturewas cooled to room temperature and filtered on a filter having a meshsize of 160 μm.

The characterization of the copolymer obtained, in terms of solidscontent (SC) and average particle size (D), is given below:

SC=25% D=40 nm Example 4 Version with Styrene

A 2 l reactor with stirrer and reflux condenser was charged with 739.5 gof deionized water and 419.3 g of 25% strength solution ofstyrene-acrylic acid copolymer, this initial charge then being heated to85° C. with stirring under a nitrogen atmosphere.

Feed stream I:

384.8 g of styrene

Feed stream II:

1.9 g of ammonium peroxodisulfate136.3 g of deionized water

When an internal temperature of 85° C. had been reached, feed stream Iand feed stream II were metered continuously into the polymerizationbatch via two separate feeds, beginning simultaneously, over a period of3 h 30, with stirring and retention of the reaction temperature. Thepumps were flushed with 318.2 g of deionized water. After the end ofboth feed streams, the system was left to afterreact at the reactiontemperature for a further 25 minutes. After that, the reaction mixturewas cooled to room temperature and filtered on a filter having a meshsize of 160 μm.

The characterization of the copolymer obtained, in terms of solidscontent (SC) and average particle size (D), is given below:

SC=24.5% D=61 nm Example 5 Version with Colloid+Surfactant

A 2 l reactor with stirrer and reflux condenser was charged with 1111 gof deionized water, 310 g of 25% strength solution of styrene-acrylicacid copolymer, and 3 grams of lauryl sulfate, this initial charge thenbeing heated to 85° C. with stirring under a nitrogen atmosphere.

Feed stream I:

387 g of methyl methacrylate

Feed stream II:

2 g of ammonium peroxodisulfate88 g of deionized water

When an internal temperature of 85° C. had been reached, feed stream Iand feed stream II were metered continuously into the polymerizationbatch via two separate feeds, beginning simultaneously, over a period of3 h 30, with stirring and retention of the reaction temperature. Thepumps were flushed with 80 g of deionized water. After the end of bothfeed streams, the system was left to afterreact at the reactiontemperature for a further 25 minutes. After that, the reaction mixturewas cooled to room temperature and filtered on a filter having a meshsize of 160 μm.

The characterization of the copolymer obtained, in terms of solidscontent (SC) and average particle size (D), is given below:

SC=24% D=50 nm Example 6 Styrene-Methyl Acrylate Copolymer

A 2 l reactor with stirrer and reflux condenser was charged with 739.5 gof deionized water and 420 g of 25% strength solution of styrene-acrylicacid copolymer, this initial charge then being heated to 85° C. withstirring under a nitrogen atmosphere.

Feed stream I:

193 g of styrene193 g of methyl methacrylate

Feed stream II:

2 g of ammonium peroxodisulfate136 g of deionized water

When an internal temperature of 85° C. had been reached, feed stream Iand feed stream II were metered continuously into the polymerizationbatch via two separate feeds, beginning simultaneously, over a period of3 h 30, with stirring and retention of the reaction temperature. Thepumps were flushed with 318.2 g of deionized water. After the end ofboth feed streams, the system was left to afterreact at the reactiontemperature for a further 25 minutes. After that, the reaction mixturewas cooled to room temperature and filtered on a filter having a meshsize of 160 μm.

The characterization of the copolymer obtained, in terms of solidscontent (SC) and average particle size (D), is given below:

SC=30.0% D=70 nm Example 7 Styrene-Maleic Anhydride as Component B

A 2 l reactor with stirrer and reflux condenser was charged with 400 gof deionized water and 750 g of 14% strength solution of styrene-maleicanhydride copolymer, this initial charge then being heated to 85° C.with stirring under a nitrogen atmosphere.

Feed stream I:

390 g of methyl methacrylate

Feed stream II:

2 g of ammonium peroxodisulfate130 g of deionized water

When an internal temperature of 85° C. had been reached, feed stream Iand feed stream II were metered continuously into the polymerizationbatch via two separate feeds, beginning simultaneously, over a period of3 h 30, with stirring and retention of the reaction temperature. Thepumps were flushed with 318.2 g of deionized water. After that, thereaction mixture was cooled to room temperature and filtered on a filterhaving a mesh size of 160 μm.

The characterization of the copolymer obtained, in terms of solidscontent (SC) and average particle size (D), is given below:

SC=29.6% D=70 nm Example 8 High Colloid Fraction

A 2 l reactor with stirrer and reflux condenser was charged with 21.1 gof deionized water and 750 g of 25% strength solution of styrene-acrylicacid copolymer, this initial charge then being heated to 85° C. withstirring under a nitrogen atmosphere.

Feed stream I:

390 g of methyl methacrylate

Feed stream II:

2 g of ammonium peroxodisulfate130 g of deionized water

When an internal temperature of 85° C. had been reached, feed stream Iand feed stream II were metered continuously into the polymerizationbatch via two separate feeds, beginning simultaneously, over a period of3 h 30, with stirring and retention of the reaction temperature. Thepumps were flushed with 80 g of deionized water. After the end of bothfeed streams, the mixture was left to afterreact at the reactiontemperature for a further 25 minutes. After that, the reaction mixturewas cooled to room temperature and filtered on a filter having a meshsize of 160 μm.

The characterization of the copolymer obtained, in terms of solidscontent (SC) and average particle size (D), is given below:

SC=44% D=80 nm Example 9 Styrene-Acrylic Acid Copolymer with Tg of about30° C.

A 2 l reactor with stirrer and reflux condenser was charged with 433 gof deionized water, and 3 grams of lauryl sulfate (30% strengthsolution), this initial charge then being heated to 80° C. with stirringunder a nitrogen atmosphere.

Feed stream I:

5 g of ammonium peroxodisulfate62 g of deionized water

Feed stream II:

400 g of styrene,260 g of butyl acrylate,10 g of methacrylic acid,11 g of surfactant solution (lauryl sulfate, 30%),384 g of deionized water

When an internal temperature of 80° C. had been reached, feed stream Iand feed stream II were metered continuously into the polymerizationbatch via two separate feeds, beginning simultaneously, over a period of4 h, with stirring and retention of the reaction temperature. The pumpswere flushed with 235 g of deionized water. After the end of both feedstreams, the system was left to afterreact at the reaction temperaturefor a further 25 minutes. After that, the reaction mixture was cooled toroom temperature and filtered on a filter having a mesh size of 160 μm.

The characterization of the copolymer obtained, in terms of solidscontent (SC) and average particle size (D), is given below:

SC=37% D=185 nm Tg=30° C. Application Examples See Appendix for GraphsTest Method

A 1.0% pulp (i.e., the beaten paper in water (blank test) or in therespective system listed below) was prepared either from 100% Espritpaper (containing two adhesive labels) or from a bleached short-fiberpulp with barcode labels. These pulp mixtures were beaten for twominutes in a mixer at room temperature (about 18° C.).

The method employed for evaluating the products was as follows: A 200 mlsample of the pulp was stirred in a 400 ml beaker at 500 rpm for 30seconds. The stickies were colored by adding to each batch a definedamount of Blue Solvent dye. After a defined stirring time, typically 2minutes, the pulp was filtered off on a 541 filter paper under constantreduced pressure. A further 541 filter paper was placed atop theresultant filter cake.

This filter paper sandwich was transferred to a Schroeter Dryer anddried on a separate metal plate at 100° C. for 15 minutes.

After cooling, the top filter paper was removed and the sticky particleswere evaluated by means of a flatbed scanner (resolution 600 dpi). UsingImageJ software, the image was analyzed (counting of the transferredstickies). ImageJ is an image processing program which can be found inthe public Java domain and can be used to draw, edit, analyze, process,store, and print images (resolution: 8-bit, 16-bit, and 32-bit). Thesoftware is able to evaluate the area and number of the stickyparticles.

The result is expressed as a % decrease relative to the blank test. Theproducts tested were inserted in the beaker before the pulp was added.System 1 is a polyvinyl alcohol; system 2 is the aqueous polymerdispersion of the invention (aqueous dispersion containing 5% ofcomponent A and 19% of component B, with component A having a glasstransition temperature of 105° C.); system 3 is an epichlorohydrin-basedfixative; and system 4 is a polyester.

Example 1

Decrease Total surface Average particle Proportion of Limit Number [%]area [mm²] size [nm] surface [%] A Blank test 157-225 102 0 2.203 0.0220.397 B 2 kg/t system 153-225 140 −37.2 3.210 0.023 0.600 1 C 2 kg/tsystem 164-222 93 8.8 1.681 0.018 0.307 2 inventive D 2 kg/t system130-223 104 −2.0 1.758 0.017 0.375 3Limit: limit value for the number of stickies, as indicated by theImageJ software (no units)Number: number of stickies on the filter paper sample (no units) %decrease: decrease (relative to blank test or untreated filter paper) inthe number of stickies, expressed as a percentage (%)Total surface area: total surface area of the filter paper sample,covered by sticky particles (in mm²)Average particle size: average particle size (in nm) of the stickiesProportion of surface (%): fraction of the filter paper sample used inthe test that is covered by stickies, expressed as a percentage (%)

Example 2

For example 2, the underlying test method was the same as in example 1.Barcode labels were used as the source of stickies.

Decrease Total surface Average particle Proportion of Limit Number [%]area [mm²] size [nm] surface [%] A Blank test 118-213 114 0 8.575 0.0751.459 B 2 kg/t system 110-209 106 7.0 11.284 0.106 1.954 1 C 2 kg/tsystem 134-208 57 50.0 3.840 0.067 0.671 2 inventive D 2 kg/t system 93-201 112 1.7 15.145 0.135 2.723 3

Example 3

Adhesive labels were used as the source of the stickies.

Decrease Total surface Average particle Proportion of Limit Number [%]area [mm²] size [nm] surface [%] A Blank test 0-206 835 0 16.6 0.021.600 B 1 kg/t system 0-205 359 57.0 6.4 0.02 0.800 2 inventive C 2 kg/tsystem 0-207 438 47.5 7.72 0.02 0.900 4 D 10 kg/t talc 0-194 557 33.39.24 0.02 1.100 E 10 kg/t 0-201 600 28.1 10.32 0.02 1.200 bentonite

Example 4

Adhesive labels were used as the source of the stickies. System 2,inventive, was compared with a latex of low Tg (Tg<40° C., system 9).

Decrease Total surface Average particle Proportion of Limit Number [%]area [mm²] size [nm] surface [%] A Blank test 0-202 499 0 10.24 0.02101.54 B 2 kg/t system 0-205 200 59.9 5.40 0.0183 0.750 2 inventive C 2kg/t system 0-199 259 48.1 5.91 0.0185 0.800 6 D 2 kg/t system 0-201 5988.2 3.94 0.0179 0.510 7 E 2 kg/t system 0-209 80 84.0 4.23 0.0183 0.6108 F 2 kg/t system 0-195 510 none 10.30 0.0203 1.580 9

1. A method for reducing the negative consequences of stickycontaminants in the processing of waste paper, which comprises the stepsof, when processing waste paper, adding an aqueous polymer dispersioncomprising a component A and a component B for coagulating anddetackifying the sticky contaminants, component A selected from thegroup consisting of a homopolymer, copolymer or its alkyl esters ofacrylic acid, methacrylic acid or its alkyl esters, styrene,methylstyrene, vinyl acetate, itaconic acid, glycidyl methacrylate,2-hydroxyalkyl (meth)acrylate, methacrylamide,N-hydroxyethyl-(meth)acrylamide, dimethacrylate monomers, 1,3-butyleneglycol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycoldimethacrylate propylene glycol dimethacrylate, dipropylene glycoldimethacrylate, 4-methyl-4-pentanediol dimethacrylate divinylbenzene,and/or trivinylbenzene and mixtures thereof, and component B is astyrene copolymer with acrylic acid, maleimide, maleic anhydride ormixtures thereof.
 2. The method as claimed in claim 1, herein componentA has a glass transition temperature >40° C.
 3. The method as claimed inat claim 1, wherein component B has a molecular weight in the range from3000 to 15 000 g/mol.
 4. The method as claimed in claim 1, wherein theaqueous polymer dispersion further comprises a component C, a cationicfixative, which promotes the coagulation of the sticky contaminates. 5.The method as claimed in claim 4, wherein component C is selected fromthe group consisting of polyethyleneimine (PEI),polydiallyldimethylammonium chloride (polyDADMAC), polyvinylamine(PVAm), polyaluminum chloride (PAC), polyacrylamide (PRAM), andpolyamine.
 6. The method as claimed in at claim 1, wherein the aqueouspolymer dispersion further comprises a component D.
 7. The method asclaimed in claim 1, wherein the water fraction of the aqueous polymerdispersion is 93% to 17.7%.
 8. An aqueous polymer dispersion forcoagulating and detackifying sticky contaminants in the processing ofwaste paper, comprising a component A which is a homopolymer, copolymeror a combination selected from the group consisting of acrylic acid oralkyl esters, methacrylic acid or its alkyl esters, styrene,methylstyrene, vinyl acetate, itaconic acid, glycidyl methacrylate,2-hydroxyalkyl (meth)acrylate, methacrylamide,N-hydroxyethyl-(meth)acrylamide, dimethacrylate monomers, 1,3-butyleneglycol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycoldimethacrylate propylene glycol dimethacrylate, dipropylene glycoldimethacrylate, 4-methyl-1,4-pentanediol dimethacrylate, divinylbenzene,trivinylbenzene and mixtures thereof, and component B, which is astyrene copolymer with acrylic acid, maleimide, maleic anhydride or amixture thereof.
 9. The aqueous polymer dispersion as claimed in claim8, wherein the aqueous polymer dispersion comprises a further componentC selected from the group consisting of polyethyleneimine (PEI),polydiallyldimethylammonium chloride (polyDADMAC), polyvinylamine(PVAm), polyaluminum chloride (PAC), polyacrylamide (PAAM), andpolyamine.
 10. The aqueous polymer dispersion as claimed in claim 8,wherein the aqueous polymer dispersion comprises a further component D.11. The aqueous polymer dispersion as claimed in claim 8, comprising 2%to 50%, of component A, 2% to 30%, of component B, 0% to 2% of acomponent C selected from the group consisting of polyethyleneimine(PEI), polydiallyldimethylammonium chloride (polyDADMAC), polyvinylamine(PVAm), polyaluminum chloride (PAC), polyacrylamide (PAAM), andpolyamine, 0% to 0.3%, of a component D, a surfactant and 96% to 17.7%of water.
 12. A composition for coagulating and detackifying thestickies in the processing of waste paper comprising an aqueous polymerdispersion including a component A and a component B, component A beinga homopolymer, copolymer or mixture thereof of methyl methacrylate,acrylate, styrene or a mixture thereof and component B being a styrenecopolymer with acrylic acid, maleimide, maleic anhydride or a mixturethereof.
 13. The composition as claimed in claim 12, wherein the polymerdispersion further comprises a component C, a cationic fixative.
 14. Themethod as claimed in claim 1, wherein component B has a molecular weightin the range from 3000 to 7000 g/mol.
 15. The method as claimed in claim1, wherein the water fraction of the aqueous polymer dispersion is 80%to 45% by weight.
 16. The aqueous polymer dispersion as claimed in claim8 comprising 5% to 30% of component A, 5% to 25% of component B, 0% to2% of a component C selected from the group consisting ofpolyethyleneimine (PEI), polydiallyldimethylammonium chloride(polyDADMAC), polyvinylamine (PVAm), polyaluminum chloride (PAC),polyacrylamide (PAAM), and polyamine, 0% to 0.2% of a component D, asurfactant and 90% to 45% of water.